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H Arita

Publications and source records attributed to H Arita.

At least 127 records · Page 7Linked to original sources
PubMed1990

Phospholipid molecular species in human umbilical artery and vein endothelial cells.

Molecular species of several phospholipid classes and subclasses were quantitatively determined in human umbilical artery and vein endothelial cells. Both types of endothelial cells were similar in phospholipid class composition, whereas they were markedly different in phospholipid subclass and molecular species composition. The amounts of two ether subclasses in phosphatidylcholine and phosphatidylethanolamine were higher in artery endothelial cells than those in vein endothelial cells. The relative content of alkylacyl subclass in phosphatidylcholine, a precursor of platelet-activating factor, was about three times higher in artery endothelial cells than in vein endothelial cells. In artery endothelial cells, arachidonic acid was in highest amounts in alkenylacyl phosphatidylethanolamine, followed by diacyl phosphatidylcholine, diacyl phosphatidylethanolamine, and phosphatidylinositol. In the vein endothelial cells, arachidonic acid was highest in phosphatidylinositol, followed by diacyl phosphatidylethanolamine, diacyl phosphatidylcholine, and alkenylacyl phosphatidylethanolamine. Artery endothelial cells had higher amounts of molecular species containing arachidonic acid than vein endothelial cells in all phospholipid classes and subclasses. These differences are thought to reflect the functional differences of artery and vein endothelial cells.

Cardiolipins↗
PubMed1989

Role of protein kinase C in U46619-induced platelet shape change, aggregation and secretion.

Stimulation of rat platelets with U46619 induced Ca2+ mobilization and platelet shape change, but aggregation and secretion were induced when platelets were stimulated with U46619 plus phorbol 12-myristate 13-acetate (PMA). However, stimulation of rabbit platelets with U46619 induced all the three platelet responses. Aggregation and secretion of rabbit platelets were enhanced by simultaneous addition of PMA and inhibited by staurosporine, but platelet shape change was not affected by them. These results suggest that protein kinase C is important for aggregation and secretion, but not for platelet shape change. On the other hand, pretreatment of platelets with PMA inhibited platelet shape change as well as Ca2+ mobilization and inositol phosphate formation, indicating that the shape change was mediated by PMA-sensitive mechanism which was not clarified.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1989

Biochemical characterization and comparison of rat thromboxane A2/prostaglandin H2 receptors in platelets and cultured aortic smooth muscle cells.

Comparison of thromboxane A2/prostaglandin H2 (TXA2/PGH2) receptors in rat cultured vascular smooth muscle cells (VSMC) with those in rat gel-filtered platelets (GFP) was carried out using a receptor-ligand binding assay. The binding of each of three radiolabeled TXA2/PGH2 receptor antagonists [( 3H]S-145,[3H]SQ29,548, and [3H]ONO3708) displayed high affinity and specificity as well as saturable and displaceable binding to a single class of recognition sites with the same maximum number in both VSMC and GFP. The Kd values for [3H]S-145 were almost identical for both VSMC and GFP, whereas the values for [3H]SQ29,548 and [3H]ONO3708 for VSMC were approximately two and six times larger than that for GFP. Kinetic analysis of the binding of each receptor antagonist revealed a smaller K1 value (the association rate constant) for [3H]SQ29,548 and a larger K-1 value (the dissociation rate constant) for [3H]ONO3708 for VSMC compared to GFP, in contrast with almost the same kinetic constants for the [3H]S-145 binding for both cells. Comparison of the inhibitory potencies (Ki values) for [3H]S-145 binding for both VSMC and GFP proved that S-145 had the same affinity for both cells; ONO11120 and BM13177, as well as SQ29,548 and ONO3708, possessed lower affinity for VSMC; and U46619 exhibited higher affinity for VSMC. The rank orders of potency were identical in both cells (S-145 greater than SQ29,548 greater than ONO3708 greater than ONO11120 greater than BM13177), which correlated well with their pharmacological activities. These results suggest a similarity in ligand binding specificity with some differences in the accessibility of the antagonists in the TXA2/PGH2 receptors between platelets and vascular smooth muscles.

Animals↗
PubMed1989

A common binding site for primary prostanoids in vascular smooth muscles: a definitive discrimination of the binding for thromboxane A2/prostaglandin H2 receptor agonist from its antagonist.

Differences in binding characteristics between agonists and antagonists for the thromboxane A2/prostaglandin H2 (TXA2/PGH2) receptor were examined in rat cultured vascular smooth muscle cells (VSMC). Scatchard analysis indicated the existence of two binding sites for the TXA2/PGH2 agonist, whereas a single class of recognition sites for the receptor antagonists were observed with approximately the same maximum binding capacity (Bmax) as a high-affinity binding site of the agonist. Weak binding inhibition by approx. 100 nM of primary prostanoids (PGE1, PGF2 alpha and PGD2) was detected only with the TXA2/PGH2 agonist, and not with the antagonist. Primary prostanoids as well as TXA2/PGH2 agonists (U46619 and STA2) suppressed the [3H]PGF2 alpha and [3H]PGE1 binding with almost the same potency, whereas TXA2/PGH2 antagonists (S-145, SQ29,548 and ONO3708) did not. The Bmax value of the binding sites was roughly identical in PGF2 alpha, PGE1 and a low-affinity binding site of U46619. These results suggest the existence of two binding sites for TXA2/PGH2 in VSMC, i.e., a high-affinity binding site corresponding to that of the TXA2/PGH2 antagonists and a low-affinity binding site in common with primary prostanoids.

Animals↗
PubMed1989

Characterization of platelet thromboxane A2/prostaglandin H2 receptor by a novel thromboxane receptor antagonist, [3H]S-145.

The specific binding sites for S-145, a novel thromboxane A2/prostaglandin H2 (TXA2/PGH2) receptor antagonist with weak partial agonistic activity, were studied in human platelet membranes. [3H]S-145 displayed high affinity and specificity, as well as saturable and displaceable binding, to a single class of recognition sites with the same maximum number of sites (2100 fmol/mg protein) as the other two TXA2/PGH2 receptor antagonists, [3H]SQ29,548 and [3H]ONO3708. Binding of S-145 to the platelet membranes was enhanced by divalent cations (Mg2+ and Ca2+), and the binding affinity in the presence of 20 mM MgCl2 was 0.75 nM, a value which was smaller than those of SQ29,548 (8.7 nM) and ONO3708 (3.7 nM). The rank order of potency (Ki) for a series of TXA2/PGH2 receptor antagonists to displace [3H]S-145 binding to the membranes was correlated with those determined from [3H]SQ29,548 or [3H]ONO3708 binding to the same preparations. Kinetic analysis for the binding of the above radiolabeled antagonist to the crude platelet membranes revealed that the dissociation rate constant (K-1) for S-145 was much smaller than that for other ligands in human, rat and rabbit platelets. The extremely slow dissociation of S-145 from the receptors may explain the long-lasting characteristic of this compound in vivo as well as the abolishment of partial agonistic activity.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1989

Possible locations of pH-dependent central chemoreceptors: intramedullary regions with acidic shift of extracellular fluid pH during hypercapnia.

Using liquid membrane pH microelectrodes, we evaluated rapid and transient changes in extracellular fluid (ECF) pH within the medulla during vertebral artery injections of CO2-saturated saline (0.5 ml) in anesthetized (Dial-urethane), spontaneously breathing cats. We found intramedullary regions where ECF pH shifted to the acid side in the time course analogous to respiratory excitation during the CO2 loadings: the acidic shift occurred just before the respiratory excitation. Since most of the tested regions showed no or few changes in ECF pH, the responsive regions are thought to be specific local environments fitting the central chemoreceptors. Forty (85%) out of the 47 responsive regions were found to be scattered in the ventrolateral medulla, i.e. a long narrow zone extending from the ventrolateral surface to the ventral respiratory group (VRG) areas where inspiratory or expiratory activity was frequently recorded. The responsive regions were not necessarily restricted to the superficial ventral layers. We were also able to find the responsive regions in the dorsal area ventral to the nucleus tractus solitarii, though they were fewer in number (7/47). The distributions corresponded rougly to the areas where we had previously identified the tonically firing neurons excited exclusively by stimulation of the central chemoreceptors. These results indicate a possibility that the pH-dependent central chemoreceptors, if any, would be located within the regions demonstrated in this study.

Animals↗
PubMed1989

Possible involvement of cytoskeleton in collagen-stimulated activation of phospholipases in human platelets.

The action of phospholipases A2 and C in the course of collagen-stimulated platelet activation and the effect of cytochalasins on the responses were studied. Stimulation of human platelets with collagen was accompanied by aggregation, Ca2+ mobilization, inositol phosphate formation, and arachidonic acid release. However, in the presence of a cyclooxygenase inhibitor or a thromboxane A2 (TXA2) receptor antagonist, collagen induced only weak arachidonic acid release and weak inositol phosphate formation. The TXA2 mimetic agonist U46619 induced all the responses except for arachidonic acid release, which was induced by synergistic action of collagen and U46619. The result that U46619 did not induce arachidonic acid release despite the activation of phospholipase C suggested that arachidonic acid was not released via phospholipase C but by phospholipase A2. These findings suggested that collagen initially induced weak activation of phospholipases A2 and C and that further activation of phospholipase C as well as Ca2+ mobilization and aggregation were induced by TXA2, whereas further activation of phospholipase A2 required the synergistic action of collagen and TXA2. Platelets pretreated with cytochalasins did not respond to collagen. Further analysis revealed that the initial activation of phospholipases A2 and C was specifically inhibited by cytochalasins, but the responses induced by U46619 or a synergistic action of collagen and U46619 were not inhibited. Therefore, we proposed that interaction of collagen receptor with actin filaments might have some roles in the collagen-induced initial activation of phospholipases.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1989

Pressor response and respiratory depression evoked by intravertebral arterial injections of hypoxic saline.

Cardio-respiratory effects of intravertebral arterial injections of hypoxic and/or hypercapnic solutions have been studied in anesthetized (dial-urethane), sino-aortic denervated, vagotomized, artificially ventilated cats. Injection of a small amount (0.8-1.5 ml) of CO2-saturated saline (hypercapnic and hypoxic loading) caused increases in arterial pressure (AP) and heart rate (HR) accompanied by an excitation of phrenic nerve activity (PNA). By contrast, injection of the same amount of N2-saturated saline (hypoxic loading) evoked dissociated cardio-respiratory effects, which were characterized by a transient depression of PNA accompanied by a small but clear increase in AP: the AP rise (18.5 +/- 6.7 mm Hg) was smaller than that (31.3 +/- 7.7 mm Hg) during the aforementioned hypercapnic and hypoxic loading with the CO2-saturated saline. The control injections (normocapnic loading) evoked negligible effects. These differences in cardio-respiratory effects suggest that there may exist hypoxia-sensitive neural substrates, independent of the central chemoreceptors, which would, directly or indirectly, influence the vasomotor center and/or the respiratory center.

Animals↗
PubMed1989

Platelet activation by tetraprenol via stimulation of phospholipase A2 action.

Only tetraprenol (n = 4), among the (n)-polyprenols studied, induced activation of rabbit platelets. Tetraprenol-induced responses, including platelet aggregation, Ca2+ mobilization, inositol phosphate formation, and arachidonic acid release, were greatly inhibited by a thromboxane A2 (TXA2) receptor antagonist and a cyclooxygenase inhibitor, indicating an essential role for endogenously produced TXA2. The TXA2-mimetic agonist U46619 induced platelet aggregation, Ca2+ mobilization and phospholipase C action but did not induce arachidonic acid release. These results suggest that arachidonic acid is not released via phospholipase C but by phospholipase A2, and this is also supported by the finding that phospholipase C action was inhibited by depletion of extracellular Ca2+, while arachidonic acid release was not. Full arachidonic acid release was found to be induced by the synergistic action of U46619 and tetraprenol. Therefore, the initial, most essential response induced by tetraprenol is a small arachidonic acid release by phospholipase A2, which results in initial TXA2 formation. Further action of phospholipase C as well as Ca2+ mobilization and aggregation were induced by the initially formed TXA2 while further activation of phospholipase A2 required the synergistic action of tetraprenol and TXA2.

Animals↗
PubMed1989

The immunosuppressive effects of the in vivo administration of endotoxin as influenced by macrophages.

It is well documented that endotoxin can have immunosuppressive effects on lymphocytes and induce the production and secretion of monokines which act on the lymphocytes. To delineate the interaction between macrophages and lymphocytes more clearly, 0.15 mg of lipopolysaccharide (LPS) (E. coli 0111:B4) was injected into Hartley guinea pigs intraperitoneally twice a day for 7 days (saline for control group). Seven days after the last injection, spleens were taken and lymphocyte proliferation was determined in the presence and absence of macrophages. When macrophages were present, there was a significant suppression of lymphocyte proliferation when PHA and PWM were used as mitogens. There was no suppression of proliferation when the macrophages were removed. Splenic macrophages were also cultured in the presence and absence of LPS and their supernatants analyzed for PGE2 and TXB2. There was no significant difference between the endotoxin and control groups for PGE2 or TXB2 production in the presence and absence of LPS. However, the endotoxin group had significant decreases in serum levels of C3 postinjection of endotoxin which could indicate C3 degradation by LPS. Taken together these results give further evidence that macrophage products in addition to PGE2 can inhibit lymphocyte proliferation. C3 degradation products could possibly stimulate macrophages to produce inhibitors of lymphocyte proliferation or induce suppressor cells.

Animals↗
PubMed1989

ECF pH dynamics within the ventrolateral medulla: a microelectrode study.

Using pH-sensitive microelectrodes, we evaluated pH dynamics of extracellular fluid (ECF) within the ventrolateral medulla (VLM) beneath the central chemoceptive areas in anesthetized, spontaneously breathing cats. Static ECF pH was acid in the superficial layers (less than 1 mm), compared with the overlying cerebrospinal fluid pH that became alkaline gradually during the experiments. In the deeper VLM areas (1-3 mm), no systematic gradients of ECF pH were observed. We found various, isolated regions where intravertebral artery injections of CO2-saturated saline evoked acidic shift of ECF pH in the time course analogous to ventilatory augmentation. Those responsive regions were found to be scattered not only in the superficial layers but also in the deeper VLM areas, although many nonresponsive regions were also intermingled among them. Occlusions of the principal vessels supplying the tested VLM regions diminished but failed to abolish the ECF pH responses to the CO2 loadings, suggesting a collateral blood flow by fine pial vessels. The present study suggests a possibility that the pH-dependent central chemoreceptors, if any, would be scattered in the deeper VLM areas as well as the superficial layers.

Animals↗
PubMed1989

Role of the mediastinum as a part of the chest wall: analyzed by computed tomography.

Using computed tomography (CT), geometrical changes in pulmonary structures in 4 human volunteers were analyzed. A series of parallel transaxial CT scans of the lung were obtained for each volunteer while he held his breath at maximal inspiration and maximal expiration. Changes in pulmonary structures were evaluated by comparing the maximal inspiration scans for each slice position. The longitudinal displacement of the lung volume was categorized as either a rib cage displacement or a diaphragm-abdominal displacement. The ratio of diaphragm-abdominal contribution to vital capacity was 0.49-0.65 for the volunteers. The thoracic volume displacement was categorized as either a mediastinal displacement or a rib cage displacement. The former was considerably larger than the latter. Since the rostral end of the mediastinum is fixed to the thoracic cage and the caudal end is fixed to the diaphragm, we conclude that the mediastinum-diaphragm boundary converts the axial force generated by the diaphragmatic excursion into radial force.

Adult↗
PubMed1989

[CD3-, OKM1+, Leu7-, Leu11+ large granular lymphocyte leukemia with ascites and CNS involvement].

A case of large granular lymphocyte (LGL) leukemia with ascites and CNS involvement was reported. A 39-year-old Japanese female was admitted to our hospital in March, 1987 because of high fever. Her clinical and hematological features were characterized by generalized lymphadenopathy, marked hepatosplenomegaly, high serum LDH level (3,257 mU/ml), marked leukocytosis (71,000/microliters) with 74% LGLs and bone marrow infiltration with 57% LGLs. Despite of chemotherapy, ascites, retroperitoneal mass and CNS involvement developed and she died of sepsis after three months. LGLs from the patient's blood, marrow and ascites, stained positively for acid phosphatase. These LGLs were E rossete+ and Fc (IgG) receptor+ and were positive for CD2, OKM1, HLA-DR and Leu11, but were negative for CD1, CD3, CD4, CD8 and Leu7 as well as for terminal deoxynucleotidyl transferase activity. The natural killer activity against K562 target cells was high and was significantly augmented after stimulation by recombinant human interleukin 2. These LGLs also demonstrated normal antibody-dependent cytotoxicity activity. Cytogenetic study on bone marrow cells and ascitic cells revealed clonal chromosomal abnormalities. These clinical, hematological, immunological and cytogenetic findings suggest that this patient had a neoplastic proliferation of natural killer cells.

Adult↗
PubMed1989

Sialyl SSEA-1 antigen as a carbohydrate marker of human natural killer cells and immature lymphoid cells.

The distribution of a carbohydrate antigen, the sialyl SSEA-1 (sialyl Lex-i), in human lymphoid cells was investigated by flow cytometry with a specific monoclonal antibody, MoAb FH-6. We concluded that the lymphocytes positive for the sialyl SSEA-1 antigen present in normal peripheral blood (PB) are natural killer (NK) cells since the positive cells had an NK activity toward K562 cells, and most of the sialyl SSEA-1+ cells were simultaneously positive for Leu-11 (CD-16) and Leu-19. Essentially, no T and B cells, defined by Leu-4 (CD3) and Leu-16 (CD20), were positive for the sialyl SSEA-1 antigen in PB samples taken from healthy donors and patients with disorders unrelated to lymphoid malignancies. Among the malignant lymphoid cells, many sialylated SSEA-1+ cells were observed in large granular lymphocyte (LGL) leukemia cells and some acute lymphoblastic leukemia (ALL) blasts, but not in CLL cells or malignant lymphoma cells. Sialyl SSEA-1 was also positive in some cultured human lymphoid cell lines. We conclude that expression of the sialyl SSEA-1 antigen is strictly limited to a distinct population of NK cells among the mature lymphocytes in normal PB, but the antigen is present in a wide range of immature lymphoblasts of T- and B-cell lineages as well as the NK-cell lineage. The sialyl SSEA-1 antigen disappears from the surface of immature lymphocytes of T- and B-cell lineages during the course of maturation.

Antibodies, Monoclonal↗
PubMed1989

[Clinical studies and sputum levels of ceftriaxone once daily administration in respiratory tract infection].

Ceftriaxone (CTRX), a new cephalosporin, was investigated by once daily administration for its clinical efficacy and safety on respiratory tract infections. The results obtained are summarized as follows: 1. Clinical responses to CTRX of a total of 39 cases with respiratory tract infections were excellent in 12 cases, good in 23, fair in 3, poor in 1 with an efficacy rate of 89.7%. Against acute bronchitis, lung abscess, bronchiectasis, chronic bronchitis and obstructive pneumonia, efficacy rates were 100%. 2. Serum levels and urinary excretion rates of CTRX were investigated in 2 cases after intravenous drip infusion of the drug at doses of 1 g and 2 g, respectively. Although urinary excretion rate tended to decrease with the deterioration of renal functions, prolongation of serum half-life was slight in those patients with normal liver function. In 1 case, it remained at 1.9 micrograms/ml at 12 hours and in another at 0.9 microgram/ml at 22 hours in sputum. According to the results, it appears that once daily administration of CTRX is effective and well tolerated in patients with acute respiratory infections.

Adult↗